Fixed IFS commands/methods crashing with paths with blanks

[sebjulliand]

Changes

Some commands/methods were not working if the IFS path they received contained blanks, namely:

• Saving an IFS file whose CCSID was not Unicode (fixed iconv call)
• Opening a terminal
• Adding a new IFS shortcut

How to test this PR

1. Create a folder with blanks in its name
2. Add its path to the IFS browser
3. Right-click and open a Terminal on it
4. Create a file in it with CCSID 850
5. Edit the file, make some changes, save it
6. Reload VSCode (the file may be in memory)
7. Open the file; changes must be kept

Checklist

• have tested my change